Purification of sugar solutions and the like



ath Oct 30,1945 2,388,223

UNITED STATES PATENT OFFICE I 2,388,223 PURIFICATION OF SUGAR SOLUTIONS AND THE mm:

Abraham Sidney Behrman, Chicago, Ill., asslgnor to Inflico Incorporated, Chicago, 111., a corporation oi! Delaware No Drawing. Application February 17, 1941, Serial No. 379,297

12 Claims. (01. 127- '-55) The present invention relates to an improved version liquor is highly acid by reason of the conprocess for the treatment of solutions containing version acid. organic substances, and has particular reference The acidity of organic solutions of this nature to an improved acid reduction process for such may be reduced by passing the solutions through solutions. a bed of an acid-adsorbent material. Various A principal object of the invention is the proacid-adsorbent materials of this nature may be vision of an acid reduction process for organic employed. For example, m-phenylene diaminesolutions of an impure nature by the use of a formaldehyde resins of the type described by bed oi anvinsoluble acid-adsorbing or removing Adams and Holmes in the Journal of Society of material and by the preliminary protective use Chemical Industry, January 11, 1935, pages 1-6T, of activated carbon. have been used for the reduction of acidity. An-

A further object of the invention is to treat imnine-aldehyde resins, guanidine formaldehyde pure acidic sugar solutions by passing the solution resins, dicyandiamide resins, and insoluble metalthrough or otherwise treating with activated carhe oxides can be used for this purpose.

. bon and then treating the solution with an acid- The utili y f anion-exchange on-r move adsorbing or acid-removing substance of solid bodies of this nature is hampered by the formaparticle form which is subject to contamination tion of impurities as solids on the bodies during by the colloidal or dissolved impuritie present the anion-exchange or removal operation. in the sugar solution upon reduction of the The exact nature of the acid removal by such acidity. bodies is not known. In some cases it appears Still another object of the invention is the that the removal is by ex han f an OH group treatment of impure organic acidic solutions with for the n tiv r l of the acid, while in other an insoluble. acid adsorbent such as resins and cases it appears that the removal i by Way of the like, whereby the acid radical in the solution absorption of the acid molecule. In either inis removed and the pH of the solution is raised stance the solution is freed from the acid and use through a range of isoelectric points of sub-- herein of the term acid-removal is intended to stances present in the acidic solution, and subinclude both type of operation. jecting the solution to a preliminary treatment The acidity of the solution may vary widely. ,In with activated carbon for removal of substances the treatment of beet sugar juices with a hydrowhich otherwise would be precipitated or removed gen exchange zeolite, the resulting solution may as an impurity upon the acid-removing body. j have a pH of the order of 2 to 3. When passed A further specific object of the invention isthe in contact with an acid-removal body, the pH of recovery of acetic acid from wood extract disthe solution will usually rise to to about neutillates, by passing the raw distillate solution trality. As the pH of organic solutions of this through activated carbon to remove impurities type rises, there is an increased tendency for mawhich otherwise would be precipitated as im- -terials in the solution to precipitate upon the purities upon an acid-removing substance, and acid-removal body; in consequence the particles subsequently passing the solution through a 1 of acid-removal material may become a water-insoluble material which has the capacity their acid-removal property lessened, their useful of absorbing the acetic acid of the solution, thereactive life greatly shortened, and they may deby removing the acetic acid from the solution in teriorate at a rather rapid rate. In addition, the a relatively pure form. entire bed tends to become fouled and inoperable. These and other objects will be evident upon a Apparently, this tendency is due at least in part consideration of the following description of a to the solution passing through an extensive preferred embodiment of the invention. series of isoelectric points of numerous impur- In many industrial processes there are proities of colloidal or dissolved nature.

duced acidic solutions of organic materials. An In accordance with the present process the disexample of such a. process is to be had in the re-. advantages which have hampered the commercial fining of beet sugar. In the acid conversion of use of these water-insoluble acid-removal bodies starch products, a slurry of starch is subjected to in the treatment of solutions of organic subthe action of hydrochloric acid or other inorstances are eliminated by treating the acidic so-' ganic acids to convert the starch to dextrose. lution with activated carbon and then contact- In this starch conversion process there are proing the solution with the water-insoluble acidduced a relatively large number of complex orremoving body. In treatment with the activated ganic bodies which are not dextrose, and the concarbon, an activated carbon of the decolorizing type is especially suitable. I prefer to use the carbon in granular form and in a bed through which the acidic organic liquor is passed. In general, the size of the carbon particles should be as a inmany cases. The depth of the carbon bed may be of the order of 2 to 4 feet. The acidic organic solution may be passed through the carbon bed at a rate of flow of the order of from 1 to 4 gallons per square foot per minute.

The treatment of the acidic organic solution with activated carbon in the manner described results in the removal from the solution of colloidal and dissolved impurities of the type which precipitate out upon the acid-removal body upon the decreasing acidity eflected by the acid-removal body in the subsequent treatment. The passage of the solution through the activated carbon does not usually eiIect a substantial change in the pH of thesolution, and the solution thereafter is passed through a suitable bed of the acidremoving material. The acid-removing treatment then is more effective by reason of the impurities which otherwise would be precipitated upon the acid-removing body having been removed by the activated carbon.

It isa characteristic of the treatment that frequent replacement of the activated carbon is not necessary. When the adsorptive capacity of the activated carbon is decreased upon continued treatment, the carbon may be regenerated or reactivated many times by simple treatment with a. solution of an alkali. Sodium' or potassium hydroxide are suitable substances for this purpose. A one-half to five per cent solution of sodium hydroxide has been found satisfactory. In the treatment of acidic beet sugar juices, I have found in certain cases that thirty gallons of one per cent caustic soda solution per cubic foot of carbon bed accomplisheseifective regeneration for a; large number of cycles.

After the acidic organic solution has been passed through the acid-removing body it generally will have a pH of '1 or more. The acidremovin body in time becomes exhausted and may be regenerated by treatment with an alkaline solution. One method which I have em. ployed to advantage consists in regenerating the acid-removal body by use of a substantial excess of alkali solution and thereafter regenerating. the activated carbon with the same solution. This eliminates the use of multiple solutions as well as multiple chemical mixing operations.

As an example of the operation of the process a beet sugar liquor treated with a hydrogen excarbon has a selective adsorption, even under very low pH conditions, for many of the impurities which would otherwise precipitate upon an boiler feed water.

increase in pH resultin from the acid adsorption.

Another example of the operation of the proc ess is to be had in the treatment of the distillate resulting from the evaporation and concentration of aqueous wood extracts. This distillate contains acetic acid and small quantities of complex organic impurities of such nature as to precipitate upon an acid-removal body when present in the solution. The condensate is passed through a bed of activated carbon and then through a bed of acid-removal material to produce an emuent of sufficient purity as to permit of its use as Additionally, the acetic acid removed by the acid-removal body can be recovered in a relatively high state of purity. The following table gives a-summary oi the results of the treatment:

The above table shows that where the condensate was directly treated with the acid-removal body the latter reduced, the color of the solution as well as the oxygen consumption value. This results in a contamination of the acid-removal body. When the solution is passed through activated carbon the analysis is indicated in column 2. It will be seen that all of the color has been removed from the solution and the oxygen consumption has been reduced from 96 to 16, the odor also having been eliminated. In column 3 is shown the analysis of the solution after passing it through the acid removal body following the activated carbon treatment. From this analysis it will beseen that the acid-removal body is not contaminated by the color constitucuts of the solution and effects no reduction in the oxygen consumption of the solution. The effectiveness of the acid-removal body is the same where activated carbon has been utilized in the preliminary treatment as where no such prelim- 'inary treatment has been given the solution.

That is, the eiiiuents in each case will have a pH of 7.1 and a similar alkalinity.

In many other industrial operations there are produced organic solutions of an acidic nature which may be treated in accordance with the invention. The impurities present generally are organic in nature and the acid to be removed may be either organic or inorganic. In all such cases the activated carbon has a. capacity of removing these substances which otherwise would precipi- 4 and different types of activated carbon are satis- 1. The process of treating impure acidic solutions containing organic material which precipitates upon change in the pH of the solution,

which comprises treating the solutions prior to treatment with a water-insoluble acid-removal body with active carbon to remove substances which would precipitate upon said water-insoluble acid-removal bodies upon contact therewith and thereafter subjecting said solution to treatment with a water-insoluble acid removal body to reduce the acidity of said solution through a range in which the separation of said substances would be enhanced if not previously removed from said solution.

2. The process of treating an acidic sugar bearing solution containing organic impurities, which comprises treating the solution with activated carbon and thereafter treating the solution with a water-insoluble acid-removal body.

3. The process of treating an impure aqueous liquid containing organic material which precipitates upon change in the pH of the solution and an acid, which comprises passing said liquid through a bed of granular activated carbon, and thereafter treating the liquid with a water-insoluble acid-removal body.

4. The process of treating an organic solution of an acid containing organic material which precipitates upon change of pH of the solution, which comprises passing said solution through a granular bed of activated carbon to remove said material and then passing said solution through a granular bed of a water-insoluble acid-removal substance.

' 5. The process of treating acetic acid-containing distillate from wood extract, which comprises passing said distillate through a bed of activated carbon to remove color and oxygen consumption substances, and thereafter passing said distillate through a granular bed of a water-insoluble acidremoval substance.

6. The process of claim 5 in which the carbon is regenerated with an alkaline solution and the acetic acid is recovered from said acid-removal substance.

'7. A process for the purification of an acidic dextrose bearing solution containing organic impurities which comprises treating the solution successively with an active carbon and an acidadsorbing body.

8. The process of treating an impure sugar solution containing colloidal impurities and an acid, which comprises treating said solution with an active carbonaceous material to remove said colloidal impurities, and thereafter treating said solution with a water insoluble acid-removal body to remove acid from said solution.

9. A process for the purification of acidic,

starch conversion, dextrose liquor comprising treating said liquor successively with an activated carbon and an acid adsorbent resin.

10. In the process of treating starch with an inorganic acid to produce a converter liquor containing dextrose resulting from conversion of the starch and containing also substantial quantities of acid and also organic impurities, the improvement which comprises treating said liquor with an active carbon to separate impurities from said liquor and thereafter treating said liquor with a water insoluble acid removal body.

11. In the process or removing acid from an acidic solution containing organic material which recipitates upon change in the pH of the solution, said process including the treatment of such solution with a water insoluble acid removal bo y. the improvement which comprises treating such solution with active carbon immediately preceding treatment with the acid removal body, whereby organic materials which would otherwise precipitate upon the acid removal body are removed by the active carbon.

12. In the processor removing acid from an acidic sugar bearing solution containing organic impurities which precipitate upon change in the pH of the solution, said process including the treatment of such sugar bearing solutions with a water insoluble acid removal body, the improvement which comprises treating such solution with an activecarbon immediately preceding treatment with the acid removal body.

ABRAHAM SIDNEY BEHRMAN. 

